Oh my god!!!! I just realised how rude that sounded... I didn't mean it was boring! I meant I was thinking about yawning and then I yawned!!!! Lol... sooo sorry!
it has to do with a lack of oxygen entering the brain (not very dangerous though)..so your mouth open somehow (probably from nerves triggering it) and you gain oxygen from the air....the reason yawning is contagious is unknown...but very interesting i think
My students yawn all the way through their singing lesson.... ! Not because they are tired or bored, but because when you sing with your soft palatte raised, this sets it off. So it is a physical thing too.
When you see others yawn, your brain tells you there is a scarcity of oxygen, so you, in turn, yawn. It's a survival technique. Like adrenaline being released in times of stress / danger etc. We have no control of that either x x